1. Field of the Invention
The present invention relates to a system and a method for controlling an exhaust gas recirculation (EGR) system.
2. Background Art
Internal combustion engines, and in particular, compression ignition (or diesel) engines have a wide variety of applications including passenger vehicles, marine vessels, earth-moving and construction equipment, stationary generators, and on-highway trucks, among others. Exhaust gas recirculation (EGR) systems have been introduced into internal combustion engines. EGR systems recirculate exhaust into the intake air stream of the engine, thereby reducing oxides of nitrogen that are formed when temperatures in the combustion chamber of the engine get too hot.
Although the EGR systems help to reduce exhaust emissions that cause smog, EGR systems cause the intake manifold air temperatures of the engine to increase to an undesirable level. Furthermore, the level of EGR is typically increased during vehicle deceleration (or decreased load conditions) and decreased during vehicle acceleration (or increased load conditions). When a diesel engine is operating in transient conditions (e.g., up and down bills, in response to a varying load, idle to rapid acceleration operation, intermittent workpiece characteristics for power takeoff driven applications, etc.), the EGR level should be varied to obtain an appropriate EGR level according to the operating conditions to maintain proper emissions reductions.
When the EGR valve is operated using an actuator, a delay occurs from when a command signal is input to the actuator to when the EGR valve starts operating. U.S. Pat. No. 6,502,563 to Itoyama discloses an EGR device which varies a target EGR amount using a routine that runs in synchronism with a crank angle sensor generated reference signal. However, the EGR control system disclosed by Itoyama can fail to properly compensate the EGR level during some operating conditions.
Thus, there exists a need and an opportunity for an improved system and an improved method for EGR control.